Axial piston variable displacement hydraulic units utilize a tiltable swashplate to control the displacement of pistons within a rotating cylinder block. One common type of tiltable swashplate is a cradle type swashplate which is supported at one end of the housing by a pair of arcuate bearings having rolling elements. Each of the pair of roller bearings is provided with a bearing cage locating the individual rolling elements of the bearing. Roller bearing geometries require the arcuate displacement of the bearing cage be in direct proportion to the arcuate displacement of the cradle swashplate in order to obtain an exclusively rolling motion of the rolling elements. Furthermore, since the roller bearings are segmental, repeated tilting of the swashplate can lead to slipping of the roller elements between the housing and the cradle swashplate to positions other than the desired optimum support positions for resisting the axial thrust of the swashplate.
In order to assure that the arcuate roller bearings do not slip to an adverse position, some of the axial piston hydraulic units have a timing or locating arrangement in the form of elongate rods or links extending between the swashplate and the housing and being connected to the cage of the cradle bearing.
One of the problems encountered with those link type locating devices is that the links either have transversely extending projections extending into mating bores in the swashplate and housing or have openings that slide onto pivot pins extending transversely from the swashplate in the housing. In both cases, the links are installed after the swashplate is installed thereby requiring an access opening provided in the side of the housing. The opening then must be covered by a removable cover with some type of seal or gasket between the housing and the cover. Providing the access unit opening, the cover and the seal adds to the cost of the unit. Moreover, the access opening provides a potential leakage path from the interior of the unit housing.
In view of the above, it would be desirable to have a simple, flexible retention mechanism which maintains synchronization between a tiltable swashplate and a bearing cage of a roller bearing supporting the swashplate, eliminates the need for an access opening in the housing, and allows blind assembly of the swashplate within the housing. Eliminating the side access openings in the housing and thus the covers therefore reduces the number of potential leak paths from the interior of the housing. Allowing blind assembly of the swashplate within the housing simplifies the assembly process.